As promised, here's the second part of a three piece blog post by Craig Anderton, we will be releasing them over the next week or so. If you value your hearing, then this is for you...
Musicians used to monitor themselves on stage with wedge monitor speakers. These sit on the floor, and direct sound upward at the performer (fig. 1). Aside from potentially leading to feedback, wedges are heavy, clutter the stage, and require their own amplification. Furthermore, being anchored to a wedge so you can monitor your sound means you can’t move around freely on stage.
Figure 1: A typical wedge monitor speaker.
Some musicians use headphones on stage—especially drummers, so they can hear a click track as well as audio from the band. However, headphones create a sense of isolation, and put up a visual barrier between the performer and audience.
The In-Ear Monitors Takeover
Given the issues involved with wedges and headphones, it’s no wonder that in-ear monitors (IEMs) have become the preferred monitoring system for performers. IEMs are small, earbud-like transducers that fit unobtrusively in your ears. They receive a monitor feed, typically from the front of house (FOH) mixer. This can be a simple wired or wireless connection, or a more complex, multichannel monitoring system with a personal mixer. Personal mixers let the performer choose a custom mix to best serve their monitoring needs. For example, a bassist might want to hear more of the drums, whereas background singers might want more lead vocal. Unlike wedges, the sound from an IEM won’t get into a performer’s mic or create feedback. That’s a huge advantage.
Furthermore, music directors can give aural cues that the audience will never hear. Bands that play to a click track can feed in some click to maintain rhythmic consistency. But most importantly, IEMs excel at hearing protection because your ears aren’t exposed to onstage volume levels. For extra protection, inserting an electronic limiter in the monitoring path can restrict levels to those considered safe for extended exposure.
IEM Options
IEMs are like miniature studio monitors, with one or more tiny drivers. These send audio to a small, thin tube that projects sound outward from the housing. The least expensive IEMs come with different, “one-size-fits-most” tips that slip over the tube. The goal of the tips is to provide a tight, yet comfortable, seal. The audio comes directly out of the tube and into your ear canal.
You’ll find two main tip types. Foam tips compress as you insert them in your ear. Once inserted, they try to expand back to their original shape. This produces a tight seal, with maximum sound isolation. Silicone tips may have a slight edge for active performers, because suction holds them in place. This makes it harder for them to fall out, but sweat can make them slippery. They’re also more durable than foam and easier to clean. Fortunately, tips are interchangeable, so you can try different types and sizes.
It’s crucial that the tip provide a tight seal. The best, although most expensive, option is an IEM tip that’s custom-fit to your ear. This generally requires going to an audiologist to have impressions made of both ears (and while you’re there, get your hearing tested). You then send the impressions to the IEM manufacturer, who creates a custom tip that provides maximum isolation and comfort. The turnaround time can be several weeks or even a few months, so take this into account if you have a big tour coming up.
A tiny bit of leakage may not be too much of a problem, and can be a worthwhile tradeoff if you can’t afford custom tips. However, significant leakage not only exposes your ears to potentially dangerous sound levels, but interferes with the accuracy with which you can monitor your audio.
The leads coming out of the IEMs matter as well. Over-the-ear wires secure the IEM in place better on your ears, and are common with higher-quality systems designed for live performance. Straight cables are more common in consumer and semi-pro IEMs.
Finally, how you insert the tips matters. Before handling IEMs, wash your hands. You don’t want dirt and bacteria going along for a ride into your ear. It's also important to keep your ears clean. If there’s wax buildup, tips could push wax deeper into the ear. Audiologists can recommend the best way to remove waxy buildup.
With silicone tips, don’t force them in. Twist them in gently and slowly to avoid putting excess air pressure on your eardrum. With foam, roll the tip between your thumb and forefinger to reduce the tip’s diameter. Then, pull up and back on your ear (using the hand from the opposite side of your body) to expose the ear canal, and push the tip in. After the gig, pull out tips slowly.
Wired or Wireless?
Mac or Windows…Strat or Les Paul…and wireless or wired IEMs. Wireless IEMs give more freedom of movement. The audio to be monitored feeds a transmitter. In smaller venues, this may be located near the mixer. In larger venues, the transmitter may be onstage, and fed with a wired connection from the mixer.
Your IEMs connect to a wireless receiver in a bodypack. A single wireless transmitter can often accommodate multiple performers, if they have their own bodypacks. Although wireless reliability and range has come a long way, flawless operation is not guaranteed in RF-laden electrical environments. Some systems are more agile at switching to an interference-free channel, or being able to choose from a wide number of channels.
Another issue is battery life and ease of replacement. Many receivers use two AA batteries, so some performers insert a new set of alkaline batteries just before a gig. This may be excessive, depending on the IEM’s current drain. Rechargeable AA batteries can be more cost-effective, because they deliver hundreds, if not thousands, of charge/discharge cycles. Some devices have built-in rechargeable batteries. So, you can recharge your IEM while you sleep, and have it ready for the next day’s gig.
Wired IEMs are more limiting with respect to moving around on stage, but you avoid dropouts, dealing with channel selection, optimizing antenna placement, and potential RF interference. What’s more, the audio fidelity is as good as whatever a wire can carry. Speaking of which…
Audio Fidelity
Wireless IEMs use analog or digital transmission technology. Analog systems tend to be less expensive, and typically use companders to reduce bandwidth requirements. All else being equal, this degrades fidelity slightly. Digital transmission can deliver high-quality audio. However, note that the receiver is either in range and works, or out of range and doesn’t work. Analog systems give you a warning, with the audio dropping out or getting fuzzier so you can scurry back in range.
Choosing analog or digital depends on your budget and needs. If you’re in a heavy metal band, a little audio compansion won’t wreck the experience. But if you’re first violinist in the Cleveland Symphony Orchestra, you might want the best possible fidelity.
IEMs are like miniature studio monitors, and for the same reasons, have different drivers for different frequencies. However, more drivers aren’t necessarily better, for the same reason that a well-designed two-way studio monitor can outperform a low-cost 3-way monitor. The important characteristics are the engineering behind the driver, and the quality of the materials being used. That said, higher-quality IEMs invariably employ more than one driver. Two- and four-driver designs are common.
IEM Tradeoffs
Although the benefits of IEMs are unquestioned, the main tradeoff is a feeling of isolation from the audience and other band members. To compensate for this, some musicians remove the IEM from one ear. This is a truly bad idea, although I guess being half-deaf is better than being totally deaf. To use IEMs and not take advantage of their ability to protect your hearing makes no sense.
Another IEM tradeoff is that they’re small. You can’t lose a wedge, but you can lose an IEM if you’re not careful. Have a dedicated case for them when not in use.
But that’s about it for tradeoffs, and there are even ways to circumvent the feeling of isolation. We’ll explore these options in another article.